Electric switch



[N VEN TOR .4 TTORNE Y S Dec. 1 2

' 19 5 B. c. PERKINS vELECTRIC SWITCH Filed Nov. 4, 1.922

` EENJvqM/N C. PERK/Ns By L/WWM Patented Dec. 1, 1925.

UNiTEo STATES PATENT oFF-ICE.

BENJAMIN C. .'PIERKINS, OF HARTFORD, CONNECTICUT, ASSIGNOR TO THE ARROWELECTRIC COMPANY, OF HARTFORD,

NECTICUT.

CONNECTICUT, A 'CORPORATION OF CON- ELECTRIC SWITCH.

Application led'November 4, 1922. Serial No. 599,015;

fo all whom, z''may concern.'

Be it known that I, BENJAMIN C. PER- KINS, a citizen of the UnitedStates of America, residing at Hartford, in the county of Hartford andState of Connecticut, have invented certain new and useful Improvementsin Electric Switches, of which the following is a specification..

vMy invention relates to electric switches, and particularly to switchesof the rotary snap type. Thev object of my invention is to provide animproved operating spring for the switch mechanism.

In the accompanying drawings y Fig. 1 is a broken side elevation of aswitch in which my invention is illustrated in one form;

Fig. 2 is a broken plan thereof;

Fig. 8 is a sidev elevation ofthe spring detached; and v Fig. 4 is aplan view of the Spring.

In switches of the rotary snap type, the standard. mechanism includes acoil spring ot' uniform diameter throughout its length, surrounding theswitch spindle and having one enld of the spring secured to the spindleor to some abutment element rotating therewith, while the other end ofthe spring engages the rotary switch blade or an associated member. Anescapement device is generally provided which retains the switch bladeduring a partial :rotation of the spinm dle, accompaniedy by acorrespondingincrease in the torsional stress ofl the spring. Uponrelease Aot the escapement, the switch blade' moves to its succeedingposition with a lsnap action. In order to obtain sufficient strength andease of action in the spring, it has been necessary to make it ofconsiderable length. In switches for controlling relatively heavycurrents, suoli as are employed in heater' installations, thenecessaryflength of the spring has often proved a serious handicap byreason of the necessarilv increased length of the s indle to accommodatethe spring, thus ren ering the switch as a whole much larger than isdesirable, bothfrom tlie standpoint of ap'- pearance and from thestandpoint of efticiency, since the lengthened spindle iinposesadditional strains upon its bearingl 1n the base, and consequentlyrenders the construction more Subject to yinjury by blows upon thehandle end of the spindle. The present invention provides an operatingspring which is not only extremely compact, but of such constructionthat it is possible to provide in a greatly restricted space, aconsiderably greater length of spring wire, with consequent increasedstrengthand durability, and freedom from the danger yof over-stressingon operation of the switch.

In the accompanying drawings, I have illustrated a rotary snap switch`of the heat` `er type, comprising an insulating base 5, .upon whichthekswitch mechanism' is mounted. The mechanism includes a rotary switchspindle 6 adaptedv to be rotated by issthe thumb piece 7, either in onedirection alone or in opposite directions, depending upon the nature ofthe escapement mecha` nisin, not show-n. Freely mounted on the spindleare switch blades 8, ofwhich two are here shown, although either more orless may be used, depending upon. the service which the switch istoperform. Rigidly associated with the switch blades is a springabutment plate 9 having an oifl set lug 10. Rigidly secured upon thespindle is a spring abutment plate 11, also having an offset-lug 12. Asshown, the lug4 12 -is spaced a less radial distance from the spindle 6than the lug 10. The' moving parts of themechanism, with the exce tionof the. thumb piece 7, are housed witliin the usual cover 13 providedwith an insulating lining 14 in a manner well under-l stood in the art.

Arranged upon the spindle 6 is the coilspring 15, to'which my inventionparticularly relates. As will be noted, the s ires of this springinstead of being of equa diameter throughout, are of unequaldiaineter,and are spaced fromeach other radially instead of longitudinally, as hashereto ore been common practice. The spircs at the opposite ends of thespring are prothereon by their engagement between the spring ends.

In the particular forni of the spring shown, the spire 18 from which theoffset end 17 extends, is ot' greater diameter than the next adjacentspire 19, which again is of greater diameter than the succeeding spire20, which finally merges in an inner spire 21, i `which is continued bya spire 22 of'mci'eased diameter, substantially corresponding to that ofthe -spire 20, while the spire 22gin turn merges into the spire 23 ofgreater diameter, and thelatter finally rinto the spire 24, which is ofa diameter substantially corresponding to that of the spire 18. Whilethe vspires are to a certain extent nested, they lie in slightly spacedplanes, so that in effect they present in side elevation the appearanceof a double cone spool, the apex angle of the cones of which is obtuse.in which the inclines of the cone meetat an angle greater than 90degrees, since this provides a spring of extremely short axial length,and thus enables me to materially shorten the length of the spindle 6,while at the same time obtaining a spring length fully as long as, ifnot longer than, that of the usually one-diameter switch spring.

The operation of the spring is substantially identical with that of theusual coil spring. Thus, when the spindle 6v is rotated by the thumbpiece 7, the lug 12, which forms the movable abutmentrigid with thespindlev 6, engages one or the other of the ends 1G or 17` of the springand shifts it cireumt'erentially with respect tothe other n spring end,which is detained by its engagement with the abutment lug 10 rigid withthe rotary switch blade. The spring is thus placed under increasedtorsional stress and effects therotation of the switch blades in theusual fashion upon the release ot the escapement which detains theblades.

I have found that the winding-up action of the spring incident to therotation of the switch spindle does not materially decrease the diameterof the innermost spire 21 of the spring, suoli reduction of diameter asvis occasioned by the winding action being confined almost entirely tothe spires of larger diameter. There is thus no danger that the springwill bind upon the switch spindle. Moreover, due to the enlargeddiameter of the end spires of the coil, and

the easier curve thereof, a spring wire ofgreater cross section may beused than has heretofore been possible. spring of greater strength maythus be used. This is important in Yconnection with multi-bladeswitches, or switches of large size, in which the load imposed u on thespring is often considerable, while 1t is particularly necessary toobtain a rapid snap action in break- Iing the currents which such largeswitches I prefer a spring are intended to handle.

It will of course be realized that the particular construction of theabutments 10v and 12 may be widely varied. Similarly it is not necessarythat the spring be in the shape of a double-cone, since it may suice insome instances to use but a single cone. In such case the end of thespring associated with the spire of least diameter may be secureddirectly to the spindle 6. I prefer, however, the double cone shapeillustrated. The number of spires may of course be varied to meet therequirements of the particular switch in which the spring is installed.

lVitli the understanding that the drawing and foregoing descriptinpresent but a single illustrative embodiment of my invention, Iclaim- 1. A coil spring for an electric switch or the like, comprising adouble cone torsion spring the terminal spiies of which are of greaterdiameter than the intermediate spires, the spire of least diameterhaving an internal diameter sufficient to freely accommodate the switchspindle, the terminal spires of the spring having o'set ends adaptedunder torsional stress to straddle and engage between them a pair ofabutinents relatively pivoted coaxial with the spindle, and angularlydisplaceable with respect to each other to place the spring underincreased torsional stress.

2. The combination with a rotary spindle, of a double cone torsionspring threaded thereon and having its opposite ends offset outwardlyaway from the spindle, a member Arigid vwith the spindle and having anabutment member engaged under stress between tlie. offset ends of thespring, together with a member pivoted on the spindle and having anabutment element engaged between said ollset ends ot' the spring andheld thereby under normal conditions in substantially radial alignmentwith the abutment member rigid with the spindle.

3. At torsion spring for an electric switch comprising a springwire'coiled to form a double cone spring with nested spires, the coil ofleastdiameter forming the common apex of the cones and spacinglongitudinally apart the next adjacent spires of greater diameter of theopposed cones the end spires of said spring terminating in olisetoutwardly extending ends adapted to embrace between them, when thespring is under slight torsional stress, relatively movable abutmeiitspivoted substantially coaxially with the spring;

In testimony whereof I have ,signed my y naine to this specification.

BENJ, G. PERKIN S.

